Laser Trip Wire Security System

Project Details

This is a very simple home security system that uses an Arduino Nano as the brains. I could have used a PIR (i will make another project with that), but I thought using a laser would be pretty cool. You can put this on either side of a doorway to be notified when someone enters a room.

Arduino Nano V3.0 - I used this because it is small and will fit on a breadboard. If i was going to make this permenant I would use an ATtiny and a PCB.

2 Breadboards - I used one for the Nano and LDR (light dependent resistor - photocell) and one for the laser.

LDR - Light Dependent Resistor - use the biggest one you can find because it will make it easier to put the laser beam on it.

2 10k Resistors and one 220Ohm Resistor - the 10k resistors will go on the LDR and the Piezo Speaker. The 220Ohm resistor is for the LED.

1 Red LED - The LED is used as a visual aid when the alarm goes off.

Jumper Wires - Since i built this on a breadboard, I used these to connect all the components to the Arduino Nano.

3v Laser Diode - You can use a ready made laser diode or pull it out of a laser pointer.

Piezo Speaker - This is what makes the noise when the laser is tripped.

STEP 2: Schematic and code

Above is the layout on the breadboard for the Arduino Nano and LDR. For the laser side, you can just attach it to a two AA battery holder and put a switch inline. I am using a 9v battery and stepping down the voltage with an LM317 Adjustable Power Supply that i made in another project. If you don't use the power supply you will only need one breadboard instead of two.